1. Field of the Invention
The present invention relates to an ultra thin manganese battery, and more particularly, to an electrode of an ultra thin manganese battery having excellent high rate properties and high energy density and a method for preparing the same.
2. Background of the Related Art
With the rapid development of electronics, telecommunications, computer industries and the like, new technologies using radio wave technology such as radio frequency identification using a radio frequency tag appears and there is a demand for batteries having various shapes, deviating from the existing standardized configuration.
Also, in the fields of cosmetics and medicines, new technologies such as iontophoresis which enables effective penetration of an objective substance into the skin attract public attention. These fields demand flexible and thin batteries with high performance as well.
In order to meet these demands, there have been continuously conducted much researches to develop new batteries and at present, an ultra thin battery, which is also called a paper battery or a sheet type battery, is spotlighted to expectedly conform to the demands.
The ultra thin battery refers to a thin cell having a sheet-like shape. It is essentially composed of an electrolyte, a cathode, an anode and a separator, like an ordinary battery. The ultra thin battery employs a sheet-shaped solid electrolyte, instead of a liquid electrolyte. Also, the electrodes and current collectors are flexible and comprise a polymer packaging material to form a soft ultra thin battery.
However, in order to prepare such an ultra thin battery, it is necessary to use an electrolyte in the gel phase. The electrolyte in the gel phase is limitedly used in special applications since its operating environment is very restricted and it shows a reduction in capacity and output during the high rate discharge due to a low conductivity, in spite of advantages in leakage and exhaustion of the electrolyte.
Also, in addition to its thinness and flexibility, it is required that the ultra thin battery have several properties such as excellent performance maintenance and leakage resistance. The ultra this battery also needs security of air-tightness between the inside and the outside of the battery since a polymer sheet as the packaging material is feeble to impact, and prevention of separation of an electrode plate caused by gas generation in the battery.
Concrete techniques related to the ultra thin battery are disclosed in the prior arts of patens or utility models. For example, U.S. Pat. No. 4,623,598 by Waki et al., discloses a thin battery enclosed in a double-layered insulation film and Japanese Patent No. 61-55866 by Fuminobu et al., discloses a thin battery prepared by adding a water-soluble polymer thickening agent to an electrolyte.
However, in general, the batteries of the above-described patents still have poor high rate properties. Also, since they are not supported by the technique of effectively controlling hydrogen gas generated during storage or discharge, in case of an ultra thin battery which is not provided with a mechanical supporter, a cathode may be separated from an anode by pressure of accumulated gas, causing sudden deterioration in performance.
In order to solve these problems, there have been presented a method for improving mechanical support property by adding a viscous polymer and a method for fundamentally suppressing the gas generation by adding mercury to increase hydrogen over-voltage. However, the former method is extremely limited in its effect and the latter method causes another problem of toxicity in terms of environmental conversation.
Further, U.S. Pat. No. 5,811,204 by Nitzan et al., and Korean Patent No. 10-0412626 disclose methods for manufacturing a battery in an open shape using a humidity controlling substance as an electrolyte to prevent gas accumulation. The operating period of the battery is too short to be practically applied in applications. Even when applicable, corrosive action of the electrolyte may cause damage of the applications. Also, the concentration of the electrolyte in the electrolyte solution is thermodynamically equilibrated with a constant relative humidity in the air. Therefore, the electrolyte flows in and out according to the humidity change in the air, which makes it difficult to guarantee the performance of the battery.
Considering the above problems, it is believed that the prior arts in the above-mentioned patents/utility models is hardly applied and realized in the actual ultra thin battery field. Therefore, there is the urgent need for a realizable novel ultra thin battery, which overcomes various defects, which obstructs the actual realization and the problems peculiar to the ultra thin battery such as poor high rate properties and deterioration in performance due to exhaustion of the electrolyte during the long-term storage or discharge.